In vehicles, either a manually or an automatically operated transmission is provided for varying the power of an internal combustion engine to a required level in accordance with traveling conditions before the power is taken off from the transmission. One such type of manual transmission is disclosed in U.S. Patent No. 5,119,917, which is incorporated herein by reference. This type of transmission may be classed as a gear type transmission, a belt type transmission, and the like, among which the gear type transmission is in widespread use because of a reduced loss of power transmission.
The gear type of the manually operated transmission includes a speed change gear train having multiple stages. The gear train is shifted using a shift lever so as to provide gear engagement at different stages. The power of the internal combustion engine is thereby varied to a required point in accordance with traveling conditions. Then, the varied power is taken off from the transmission.
The aforesaid gear type of the manually operated transmission may be classified as, e.g., a selective sliding gear type, a constant mesh type, and the like, depending on how a speed change ratio is varied.
The selective sliding gear type of the manually operated transmission has respective gears mounted on a main shaft, a counter shaft, and a reverse idler shaft. The main shaft is an input shaft which is connected to and disconnected from the internal combustion engine by means of a clutch on the engine side. The counter shaft and the reverse idler shaft extend substantially parallel to the main shaft. A reverse idler gear, which is mounted on the reverse idler shaft, is slidingly driven into engagement with both a reverse main gear and a sleeve gear which are positioned respectively on the main shaft and the counter shaft, thereby transmitting the power thereto from the engine. In addition, this type of transmission is constructed to allow the reverse idler gear to be operational, even when a vehicle remains stationary.
In the constant mesh type of the manually operated transmission, pairs of gears corresponding in number to necessary speed change stages are constantly engaged with each other. Further, the transmission is designed to permit an idle operation between the shafts and the gears. In order to achieve torque transfer, the pairs of gears providing the required speed change ratios are fixed to the shafts by means of coupling sleeves that are mounted on the shafts.